In the world of fitness–as in the world of physics–there is a difference between strength and power.
Muscle strength is the maximum amount of force a muscle can exert against resistance in a single effort. For instance if a person is able to press 135 lbs in a single rep of a bench press, that would be their muscle strength.
Muscle power, on the other hand, is the ability to exert maximal force in as short a time as possible; this could mean accelerating (as in a run), jumping or throwing an object (a ball, a discus, a javelin). Muscle power takes into account speed.
The way a person trains their muscles depends on the outcome they are looking for. Those seeking sports performance often focus on power training since speed is usually a factor in competitive sports. Many others who look to improve muscle tone or who want to be able to carry out activities of daily living may focus on strength training.
The most recent issue of ACE Fitness Journal (Sept. 2019) had a brief article on power training vs strength training for older adults by Shirley Archer, JD, MA. She reports on a study out in Brazil reporting on the benefits of power training in an older population. It showed that subjects in the study who were above the median in maximal power had better survival rates than those below the median; in other words, if you have more muscle power there is a tendency to live longer.
This is exciting news to those of us who work with many older clients. The study can be found in https://journals.lww.com/nsca-scj/pages/default.aspx, vol. 41, issue 1.
The article by Archer notes that there is need for more study and caution. Power training requires more balance and coordination; some seniors may not have the necessary skills to perform power training. Even so, it is interesting to note that this is a promising direction for trainers and clients as we age.
I look forward to more research as I continue to help my older clients live longer, healthier and more independent lives.